1. Field of the Invention
The present invention relates to wellbore tools which provide selective fluid communication with subterranean wellbore zones, and which are especially useful in delivering production-enhancing fluids to a particular producing zone.
2. Description of the Prior Art
In the completion and work over of producing oil and gas wells, it is frequently necessary to selectively communicate fluids between a workstring and one particular region of the wellbore, to the exclusion of other regions of the wellbore. Typically, such operations involve the selective delivery of production-enhancing fluids to a target zone. Such fluids may wash debris from the region of the wellbore which is adjacent the target zone, may clear a flow path from a producing zone to a region of a wellbore, or may stimulate production from oil and gas bearing formations by altering the chemical or mechanical properties of either the producing formation itself or the oil and gas deposits contained therein. Such operations include acidizing, washing, and fracturing of the oil and gas producing formations. Of course, it is not efficient to deliver the production-enhancing fluids to all regions of the wellbore when only a particular region needs the treatment. Therefore, washing tools have been developed which isolate a region of a wellbore which is in communication with a selected zone of interest, and which allow for the selective delivery of product-enhancing fluids to that particular zone.
It is also frequently desirable to selectively remove fluids from a particular zone in a producing oil and gas wellbore. The removal of fluid is particularly useful in testing and sampling operations to establish flow rates, water cut, and production volume from a particular zone. Of course, if the fluid from the zone of interest mixes with fluids from other regions of the wellbore, meaningful testing and sampling operations can not be obtained. Prior art tools exists which allow for the selective sampling and testing of fluids from a target zone.
Typically, the prior art devices for communicating fluids between a workstring and a selected wellbore zone include isolator members which are coupled to a housing which is carried exteriorly of a workstring. The isolator members do not move freely with respect to the workstring, and thus may become damaged when the tool is run into a wellbore, particularly when the wellbore is deviated, horizontal, or contains "dog leg" bends. It is a common practice to custom manufacture such tools with the isolator members spread apart a selected distance to accommodate a particular zone length. It is common for these tools to be lengthy and cumbersome to manipulate. They are also quite expensive since substantial amounts of material are required to fabricate the elongated housing to which the isolator members are attached.